The seas rise, the glaciers disappear

Between Greenland and the Faroe Islands there is an undersea waterfall 30 times the size of the River Amazon. The water cascades over a submarine ridge, then rumbles down the ocean floor all the way to the Cape of Good Hope. This current is a result of the high salt content of the surface of the North Atlantic. The salty water, being denser than the water underneath, sinks and starts to travel. The global circulation system this flow initiates ensures that warm water travels back from the Caribbean to western Europe. Were the North Atlantic to become less salty, in other words, the currents keeping Europe warm would slacken.

Eight and a half thousand years ago, an ice shelf damming two vast glacial lakes in North America exploded. The lakewater rushed through the Hudson Strait, mingling with the salty waters of the Atlantic. The result was a 200-year ice age, during which humans became extinct in northern Europe. In Greenland today, just to the north of the great Atlantic waterfall, scores of glaciers and ice-dammed fjords are beginning to melt. Over the past 20 years, an area of Arctic sea ice the size of Texas has disappeared. As the ice retreats, the pole becomes darker, absorbing more heat and accelerating the melting. The North Atlantic could become significantly wetter.

It is not clear what the results will be. The dilution of the ocean is most likely merely to slow the warming of western Europe. But there remains a possibility that it could cause a sudden drop in temperature so severe that Britain would, once more, become uninhabitable.

If this happens, then, calamitous as it will be, at least a kind of mortal justice will have been done. For, in the absence of a new ice age, the effects of global warming promise to be cruelly ironic: the impact of fossil fuel consumption will be most severe in precisely those regions of the world in which the least fossil fuel has been consumed. The arid parts of sub-Saharan Africa, for example, are becoming still drier: in East Africa, droughts of the kind which used to strike every 40 years are now arriving every four or five. The famines of the next 20 years will surpass any the world has seen before.

On the Indian sub-continent, the great centres of both population and food production are the valleys of the Ganges, the Brahmaputra and the Indus, all of which are fed by Himalayan glaciers. The glaciers are retreating so fast that the rivers may dry up in the summer by 2040. The results, if this happens, will be catastrophic. Bangladesh will be hit twice, as the people of the river deltas are driven off their lands by rising sea levels.

These projections make Britain's current "refugee crisis" look trifling. Already, according to the Red Cross, environmental refugees outnumber the people displaced by conflict and oppression. This week Sajeeda Choudhury, the Bangladeshi environment minister, told the BBC that climate change would leave her country with 20m environmental refugees. The rich nations would have to "rethink their immigration policies". The British environment minister, Michael Meacher, agrees: "We may have to do what Mrs Choudhury asks," he said.

The distinction between political and economic refugees has always been an artificial one: the poorest regions of the world remain poor largely as a result of the policies of rich nations. But in this case our moral responsibility is incontestable, if somewhat difficult to comprehend: every time you turn on your kettle in Birmingham, you are helping to flood Bangladesh. Global warming requires a wholly new ethical framework, one which classifies actions which have hitherto seemed innocent as deadly.

There is nowhere else for the displaced people of Bangladesh or sub-Saharan Africa to go. The cities have nothing to offer them: there will be no industrial revolution in these regions. If we don't let them in, they will die, and we, the consumers of fossil fuels, will be responsible. If global warming is not contained we will be faced with a choice of a refugee crisis of unimaginable proportions, or direct complicity in crimes against humanity.

The alternative is to reduce our carbon consumption not, as the world's rich nations envisage, by 10 or 20%, but by 90%, within the next 10 years. This may sound impossible. But there are hardly any western economic activities whose impact cannot be cut to this extent, either through technological change or through reduced consumption, without causing serious damage to the quality of life.

What this requires is radical thinking of a kind no government has yet been willing to contemplate: the abandonment of GDP as the index of prosperity, direct confrontation with the most powerful industrial lobbies on earth, a re-regulation of the market to force both producers and consumers to carry their own costs. Is any government brave enough to do this? Is any government brave enough not to?